Generally conventional automatic transmissions include a torque converter to transfer engine torque from an engine to an input of the transmission, planetary gearsets that provide various gear ratios of torque and thus various drive speeds, and fluid pressure-operated, multi-plate drive or brake clutches and/or brake bands that are connected to the individual elements of the planetary gearsets in order to perform gear shifts between the various gear ratios.
In addition, conventional automatic transmissions include one-way clutches that cooperate with the multi-plate clutches to optimize power shifts and a transmission controller for selectively applying and releasing elements to shift the gears. For example, the controller chooses the proper gear depending on system conditions such as the shift-program selected by the driver (i.e., Drive, Reverse, Neutral, etc.), the accelerator position, the engine condition, and the vehicle speed.
As an accelerator is further depressed, and the vehicle increases speed, the controller disengages and engages appropriate clutches to sequentially shift up through each of the gears until the highest (e.g., fifth) gear is engaged. Once a gear is engaged, further depression of the accelerator will cause the controller to operate a downshift of the transmission such that a lower gear is chosen. In so doing, the controller will shift down through the gears sequentially. In other words, the transmission will run through each of the next successively lower gears prior to reaching the lowest desired gear.
Thus, conventional transmissions suffer from the disadvantage of requiring sequential movement through each of the gears in the transmission. Furthermore, conventional transmissions suffer from the disadvantage of limiting gear choices to only those gears in the sequential chain.
Therefore, a transmission having both a sequential gear set and an alternate gear set capable of providing additional gear ratios is desirable in the industry. Furthermore, a transmission having a controller capable of shifting between the sequential gear set and the additional gear set, to provide the transmission and vehicle with the optimum gear selection, is also desirable.